Gunfright: Routine at BFDB

Draws the columns of a sprite which is flipped and shifted. There is a piece of code for each of up to five columns of the sprite, and the code for the width of the sprite is where the jump at SpriteJumpOpcode starts. Each piece puts a column into two bytes of the buffer, using the table for the shift to turn the mask and the pixels round and split them in two. It works from right to left.

Draws the columns of a sprite which is flipped and shifted. There is a piece of code for each of up to five columns of the sprite, and the code for the width of the sprite is where the jump at SpriteJumpOpcode starts. Each piece puts a column into two bytes of the buffer, using the table for the shift to turn the mask and the pixels round and split them in two. It works from right to left.
The jump at SpriteJumpOpcode starts here for five columns.
DrawFlippedShiftedColumns	BFDB	CPL	Invert the screen byte.
	BFDC	POP DE	Restore the mask into E and the pixels into D from the stack.
	BFDD	LD L,E	Clear the screen bits under the part of the mask which is in this byte.
	BFDE	OR (HL)
	BFDF	CPL
	BFE0	LD L,D	Add the part of the pixels which is in this byte.
	BFE1	OR (HL)	Add the part of the pixels which is in this byte.
	BFE2	LD (BC),A	Store the byte and move on to the byte on the left.
	BFE3	DEC BC	Store the byte and move on to the byte on the left.
	BFE4	DEC H	Point H at the table for the bits which move into the next byte, and fetch that screen byte.
	BFE5	LD L,E
	BFE6	LD A,(BC)
	BFE7	CPL	Clear the screen bits under the part of the mask which has moved into it.
	BFE8	OR (HL)
	BFE9	CPL
	BFEA	LD L,D	Add the part of the pixels which has moved into it.
	BFEB	OR (HL)	Add the part of the pixels which has moved into it.
	BFEC	INC H	Point H back at the first table.
The jump at SpriteJumpOpcode starts here for four columns.
	BFED	CPL	Invert the screen byte.
	BFEE	POP DE	Restore the mask into E and the pixels into D from the stack.
	BFEF	LD L,E	Clear the screen bits under the part of the mask which is in this byte.
	BFF0	OR (HL)
	BFF1	CPL
	BFF2	LD L,D	Add the part of the pixels which is in this byte.
	BFF3	OR (HL)	Add the part of the pixels which is in this byte.
	BFF4	LD (BC),A	Store the byte and move on to the byte on the left.
	BFF5	DEC BC	Store the byte and move on to the byte on the left.
	BFF6	DEC H	Point H at the table for the bits which move into the next byte, and fetch that screen byte.
	BFF7	LD L,E
	BFF8	LD A,(BC)
	BFF9	CPL	Clear the screen bits under the part of the mask which has moved into it.
	BFFA	OR (HL)
	BFFB	CPL
	BFFC	LD L,D	Add the part of the pixels which has moved into it.
	BFFD	OR (HL)	Add the part of the pixels which has moved into it.
	BFFE	INC H	Point H back at the first table.
The jump at SpriteJumpOpcode starts here for three columns.
	BFFF	CPL	Invert the screen byte.
	C000	POP DE	Restore the mask into E and the pixels into D from the stack.
	C001	LD L,E	Clear the screen bits under the part of the mask which is in this byte.
	C002	OR (HL)
	C003	CPL
	C004	LD L,D	Add the part of the pixels which is in this byte.
	C005	OR (HL)	Add the part of the pixels which is in this byte.
	C006	LD (BC),A	Store the byte and move on to the byte on the left.
	C007	DEC BC	Store the byte and move on to the byte on the left.
	C008	DEC H	Point H at the table for the bits which move into the next byte, and fetch that screen byte.
	C009	LD L,E
	C00A	LD A,(BC)
	C00B	CPL	Clear the screen bits under the part of the mask which has moved into it.
	C00C	OR (HL)
	C00D	CPL
	C00E	LD L,D	Add the part of the pixels which has moved into it.
	C00F	OR (HL)	Add the part of the pixels which has moved into it.
	C010	INC H	Point H back at the first table.
The jump at SpriteJumpOpcode starts here for two columns.
	C011	CPL	Invert the screen byte.
	C012	POP DE	Restore the mask into E and the pixels into D from the stack.
	C013	LD L,E	Clear the screen bits under the part of the mask which is in this byte.
	C014	OR (HL)
	C015	CPL
	C016	LD L,D	Add the part of the pixels which is in this byte.
	C017	OR (HL)	Add the part of the pixels which is in this byte.
	C018	LD (BC),A	Store the byte and move on to the byte on the left.
	C019	DEC BC	Store the byte and move on to the byte on the left.
	C01A	DEC H	Point H at the table for the bits which move into the next byte, and fetch that screen byte.
	C01B	LD L,E
	C01C	LD A,(BC)
	C01D	CPL	Clear the screen bits under the part of the mask which has moved into it.
	C01E	OR (HL)
	C01F	CPL
	C020	LD L,D	Add the part of the pixels which has moved into it.
	C021	OR (HL)	Add the part of the pixels which has moved into it.
	C022	INC H	Point H back at the first table.
The jump at SpriteJumpOpcode starts here for one column.
	C023	CPL	Invert the screen byte.
	C024	POP DE	Restore the mask into E and the pixels into D from the stack.
	C025	LD L,E	Clear the screen bits under the part of the mask which is in this byte.
	C026	OR (HL)
	C027	CPL
	C028	LD L,D	Add the part of the pixels which is in this byte.
	C029	OR (HL)	Add the part of the pixels which is in this byte.
	C02A	LD (BC),A	Store the byte and move on to the byte on the left.
	C02B	DEC BC	Store the byte and move on to the byte on the left.
	C02C	DEC H	Point H at the table for the bits which move into the next byte, and fetch that screen byte.
	C02D	LD L,E
	C02E	LD A,(BC)
	C02F	CPL	Clear the screen bits under the part of the mask which has moved into it.
	C030	OR (HL)
	C031	CPL
	C032	LD L,D	Add the part of the pixels which has moved into it.
	C033	OR (HL)	Add the part of the pixels which has moved into it.
	C034	INC H	Point H back at the first table.
	C035	LD (BC),A	Store the last byte of the row.
Continue on to FinishFlippedSpriteRow.